Membrane Phospholipids: The Key Regulator of Tissue Factor Encryption/Decryption

膜磷脂：组织因子加密/解密的关键调节剂

• 批准号: 9054915
• 负责人: Vijaya Mohan Rao Lella
• 金额: $ 36.25万
• 依托单位: UNIVERSITY OF TEXAS HLTH CTR AT TYLER
• 依托单位国家: 美国
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-09-01 至 2019-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9054915
• 关键词: 4 hydroxynonenal; Acute myocardial infarction; Affect; Aldehydes; Binding; Biochemistry; Blood Coagulation Disorders; Blood Coagulation Factor; Blood Vessels; Blood coagulation; Cell Surface Receptors; Cell membrane; Cell surface; Cells; Coagulants; Coagulation Process; Complex; Data; Dependency; Development; Disease; Disulfides; Endothelial Cells; Equilibrium; Event; Excision; Exhibits; Factor VIIa; Fatty Acids; Generations; Glycoproteins; Health; Hemostatic Agents; Hemostatic function; Hydrolysis; Inflammation; Injury; Integral Membrane Protein; Interphase Cell; Investigation; Ischemic Stroke; Knowledge; Lipid Peroxidation; Liposomes; MAP Kinase Gene; MAPK14 gene; Maintenance; Malignant Neoplasms; Mechanics; Mediating; Membrane; Membrane Lipids; Membrane Microdomains; Metabolism; Molecular; Oxidative Stress; Pathogenesis; Pathway interactions; Phosphatidylserines; Phospholipids; Plasma; Play; Prevention strategy; Process; Protein Disulfide Isomerase; Reaction; Reactive Oxygen Species; Regulation; Role; Signal Pathway; Signal Transduction; Sphingomyelins; Stimulus; Sulfhydryl Compounds; Surface; System; TXN gene; Testing; Thromboplastin; Thrombosis; Thrombus; Unstable angina; cell injury; cell type; cofactor; design; effective therapy; encryption; improved; insight; macrophage; novel; novel therapeutic intervention; oxidation; research study; response; rho; treatment strategy

 DESCRIPTION (provided by applicant): The coagulation cascade is initiated by binding of coagulation factor VIIa (FVIIa) to its cell surface receptor, tissue factor (TF). Tissue factor is essential for hemostasis, but the aberrant expression or activation of TF leads to thrombosis, the precipitating event in acute myocardial infarction, unstable angina, and ischemic stroke. It also contributes to inflammation and cancer. Therefore, the proper regulation of TF expression and the activity is critical for not only to maintenance of the hemostatic balance, but also for health in general. Interestingly, the majority of TF on cell surfaces exists in a cryptic state, i.., with no or little coagulant activity, despite forming complex with FVIIa. A stimulus is required fo cryptic TF to become procoagulant active form. A variety of cellular alterations transforms cryptic TF to coagulant active TF. Our recent studies show that 4- hydoxynonenal (HNE), one of the most abundant and bioactive species produced by the lipid peroxidation, activates TF in monocytic and endothelial cells. At present, it is unclear how the coagulant active TF differs from the cryptic form or mechanics involved in TF encryption and decryption. It is unknown, at present, whether phospholipids present in the outer leaflet of plasma membrane play a critical role in maintaining TF in the cryptic state. Of all the proposed mechanisms, externalization of anionic phospholipids at the outer leaflet of plasma membrane following cell activation appears to be the main mechanism for transformation of the cryptic TF into active TF. However, other mechanisms, such as protein disulfide isomerase (PDI)-mediated thiol-disulfide exchange reactions, may also play an important role in TF activation in certain cell types. Mechanisms responsible for maintaining TF in a cryptic state in naive cells and molecular pathways responsible for exposure of anionic phospholipids in response to pathophysiologically relevant stimuli are unknown. The following specific aims are designed to fill these gaps of the knowledge on the regulation of TF activity at the cell surface. Aim 1: Test a novel hypothesis that high sphingomyelin content in the outer leaflet of the plasma membrane is responsible for maintaining TF in its cryptic state at the cell surface. Here, we will also test that the hydrolysi of sphingomyelin in the plasma membrane plays a key role in TF decryption; Aim 2: Elucidate signaling mechanism(s) involved in externalization of phosphatidylserine and TF activation by HNE, and ascertain contribution of PDI-mediated thiol-disulfide exchange pathways and lipid raft integrity in this process. To strengthen observations made in cell systems, and to have better understanding of how cell membrane lipids influence TF activity, we will also perform additional studies with purified TF incorporated into defined liposomes. The data obtained from the proposed studies will provide new insights into understanding of the regulation of TF activity on cell surfaces. Overall, the knowledge gained from the proposed studies will be helpful in understanding the pathogenesis of thrombotic disorders and will be useful in designing better treatment strategies for both thrombotic and hemorrhagic diseases.

 描述（由申请人提供）：凝血级联是通过凝血因子VIIa（FVIIa）与其细胞表面受体组织因子（TF）结合而启动的。组织因子对于止血至关重要，但 TF 的异常表达或激活会导致血栓形成，这是急性心肌梗塞、不稳定型心绞痛和缺血性中风的诱发事件。它还会导致炎症和癌症。因此，正确调节 TF 表达和活性不仅对于维持止血平衡至关重要，而且对于整体健康也至关重要。有趣的是，细胞表面上的大多数 TF 以隐秘状态存在，即，尽管与 FVIIa 形成复合物，但没有或几乎没有凝血活性。隐性 TF 需要刺激才能变成促凝血活性形式。多种细胞变化将隐秘的 TF 转变为具有凝血活性的 TF。我们最近的研究表明，4-羟基壬烯醛 (HNE) 是脂质过氧化产生的最丰富和生物活性物质之一，可激活单核细胞和内皮细胞中的 TF。目前，尚不清楚促凝剂活性 TF 与 TF 加密和解密所涉及的神秘形式或机制有何不同。目前尚不清楚质膜外叶中存在的磷脂是否在维持 TF 隐秘状态中发挥关键作用。在所有提出的机制中，细胞激活后质膜外层阴离子磷脂的外化似乎是隐性 TF 转化为活性 TF 的主要机制。然而，其他机制，例如蛋白质二硫键异构酶 (PDI) 介导的硫醇-二硫键交换反应，也可能在某些细胞类型的 TF 激活中发挥重要作用。负责在幼稚细胞中维持 TF 处于隐秘状态的机制以及负责暴露阴离子磷脂以响应病理生理学相关刺激的分子途径尚不清楚。以下具体目标旨在填补细胞表面 TF 活性调节的知识空白。目标 1：测试一个新的假设，即质膜外叶中的高鞘磷脂含量负责维持 TF 在细胞表面的隐秘状态。在这里，我们还将测试质膜中鞘磷脂的水解在TF解密中起着关键作用；目标 2：阐明 HNE 使磷脂酰丝氨酸外化和 TF 激活所涉及的信号传导机制，并确定 PDI 介导的硫醇二硫键交换途径和脂筏完整性在此过程中的贡献。为了加强在细胞系统中进行的观察，并更好地了解细胞膜脂质如何影响 TF 活性，我们还将利用纯化的 TF 掺入特定的脂质体中进行额外的研究。从拟议研究中获得的数据将为理解细胞表面 TF 活性的调节提供新的见解。总体而言，从拟议研究中获得的知识将有助于了解血栓性疾病的发病机制，并将有助于为血栓性疾病和出血性疾病设计更好的治疗策略。